Aperture distributions have been measured using replicas of apertures to investigate the effect of variable aperture on solute transport in five transparent fracture samples. The coefficient of variation (Cv), correlation length (λ), and anisotropy ratio (AR) were used to quantify the aperture distributions. Step-type tracer tests showed that dispersion is significantly influenced by both λ and Cv. Dispersivity (α) increases with λ and Cv. The magnitude of α is proportional to a polynomial function of natural logarithm of Cv2 and is linearly proportional to λ and the total sill measured from the semivariogram. The effect of AR is insignificant to those of the other parameters on α. Despite assumptions of the small perturbation theory developed by Gelhar <1993>, the prediction of α from the theory is similar to α measured in this study. If the small perturbation theory is valid and reliable data for the tailing in a breakthrough curve are obtained, the analysis of the curve by the moment method gives a more reliable result than by the conventional fitting of a one-dimensional analytical solution to the curve.